Rahu (north lunar node) and Ketu (south lunar node) are not real planets, but they carry immense power in KP. They are agents—stand-ins for planetary significations they occupy or lord.
Agent rule: Rahu/Ketu inherit the significations of the planet whose sign they occupy. If Rahu is in Virgo, Rahu acts as an agent for Mercury (Virgo's lord). If Ketu is in Scorpio, Ketu acts as an agent for Mars (Scorpio's lord, in classical; or Mars+Ketu in KP, requiring the stronger of the two).
Influence modifier: Rahu is amplifying, destabilizing, foreign-bringing, illusion-generating. Ketu is separating, releasing, past-related, spiritual. An event governed by Rahu often manifests as unexpected, comes from outside, or involves a detour. An event governed by Ketu often involves endings, release, or spiritual learning.
Example: 7th house (marriage) cuspal sub-lord is Rahu (acting as Mercury agent). Marriage might come through communication, a foreign country, or unexpected connection. But Rahu's involvement suggests delay or an unconventional path.
Hierarchy: If Rahu tenants a house but the planet it agents for does not, Rahu's promise overrides. But if both Rahu and the agented planet are present, Rahu's influence modifies the planet's promise (often by delaying or complicating it).
The engine identifies Rahu and Ketu's agented planets and flags their involvement in significator outcomes. You will learn to incorporate Rahu/Ketu's shadowiness into your predictions, upgrading from "marriage will happen" to "marriage will happen, likely via a foreign connection or unconventional meeting."